Abstract The Proteomics Core Facility provides protein identification and characterization services to about one third of all investigators performing diabetes-related research at the University of Massachusetts. The laboratory is a well established self-supporting facility located on the Worcester Foundation Campus of the University. It provides services to investigators not only at UMass but also to many extramural academic institutions and corporations. The laboratory is equipped with the latest instrumentation for protein/peptide mass spectral analysis. These instruments provide precise mass measurements on both intact proteins and peptides derived from proteolytic digests. In addition, these instruments allow for controlled fragmentation of individual peptides to derive further structural information. Since the genomes of many model organisms are completed the sequences of the various expressed protein products (Proteome) are readily available in public databases. Mass spectrometry has become one of the primary methods for identifying and characterizing proteins of biological interest. The method relies on comparing precisely measured mass values derived from proteolytic peptides or their generated fragments with theoretically calculated values obtained from various databases using specific cleavage rules. Many DERC investigators are studying the proteins that are involved in signal transduction pathways {i.e. the mechanism of insulin action) as well as the polypeptide components of larger multisubunit structures (i.e. the ciliary structures of pancreatic islet cells). The Proteomics Core provides DERC investigators with a centralized laboratory that gives them priority services at highly subsidized rates. Importantly, it also provides face to face consultations on data interpretation as well as sample preparation. This speeds up the characterization of proteins, allowing projects to move along at a more rapid pace.